Control instrument



Dec. 1, 1942. c. B. MOORE CONTROL INSTRUMENT Original Filed May 23, 19392 Sheets-Sheet l INVENTOR v COLEMAN BJIOORE 56 BYP, P

ATTORNEY l, 1942. c. a. MOORE CONTROL INSTRUMENT Original Filed May 23,1939 2 Sheets-Sheet 2 A TO NEY E R o o M B N A M E L o c Patented Dec.1, 1942 CONTROL INSTRUIHENT Coleman B. Moore, Carroll Park, Pa.,assignor to The Brown Instrument Company, Philadelphia, Pa., acorporation of Pennsylvania Original application May 23, 1939, SerialNo.

275,206. Divided and this application December 9, 1939, Serial No.308,435

7 Claims. (Cl; 137-144) The present invention relates to controlinstruments and more particularly to those instruments known as "aircontrollers in which the variation of the value of a condition is usedto change the regulating pressure of an actuating fluid that is used tocontrol the position of a valve or other regulating apparatus.

It is an object of the present invention to provide a pilot valve whichis responsive to the condition being measured and regulate the controlpressure applied to the control element.

It is a further object of my invention to provide a pilot valve of thenon-leak type or one in which the admittance or exhaust of the actuatingfluid from the valve is not permitted except at the time of a change inthe value of the condition being measured. This has the advantages.

of maintaining the pressure in the system at a constant value and of notusing any of the actu ating fluid except at times of change in thecondition.

It is a further object of the invention to provide a control systemwhich utilizes one or more pilot valves to regulate the control pressureapplied to the control element.

The present invention isa division of my copending application SerialNumber 275,206 filed May 23, 1939. That application is concerned moreparticularly with the flow control system while the present case isdirected more particularly to the pilot valves that are used in thesystem. While I will describe my invention in connection with thecontrol of a fluid flowing through a conduit it is obvious that it maybe used in the control of other variables wherein the same conditionexists. v

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages and specific objects obtained with its use,reference should be had to the accompanying drawings and descriptivematterin which I have illustrated and described a preferred embodimentof the invention.

In the drawings:.

Fig. l is a view, partly in section, showing one form that my inventionmay assume;

Fig. 2 is a section view taken on line 2-2 of Fig.

Fig. 3 is an enlarged view of the nozzle in the pilot valve; v

Fig. 3A is. an enlarged view of the nozzle taken on line A-A of Fig. 3;

Fig. 4 is a perspective view of .certain levers shown in Fig. 1; and

Fig.5isaviewofa system.

Referring now to Fig. 1, there is shown a pipe I the flow through whichis to be measured and controlled. Located in the pipe is a valve 2 whichis normally biased to a closed position by a spring but may be open dvarious amounts by varying the pressure of air, or other suitable gas,applied to the top of a diaphragm attached to the valve stem. Located inthe pipe I, downstream of the valve, is an oriflce 3, the pressure dropacross which is used to determine the flow. The pressure drop ismeasured by a manometer l of any commercial design, but preferably ofthe type shown in Patent 1,743,852 granted to Thomas R. Harrison. Inthis manometer the difierential pressure across the orifice is impressedupon the sealing liquid 5, the level of the liquid in either leg of themanometer forming a measure of the fluid rate of flow. A float on theliquid in one of the manometer legs rises and falls with the sealingliquid and carries an armature 6 adapted to cooperate with inductioncoils I and la. forming the transmitting element of a distant readingsystem. The receiving element of this system includes receiving coils 8and 8a electrically connected to the transmitting coils and inductivelyrelated to a receiving armature 9, which as more fully described in theabove mentioned patent, is thereby given movements corresponding tomovements of the armature 6 carried by the manometer float.

The coils 8, 8a are located in any suitable instrument casing l0, shownherein as being circular in shape, that is provided with a door having aglass window therein. The coils 8, .011 along with other parts to bedescribed, are preferably covered by plates II and A through whichproject a chart supporting hub II, a pen arm l3, upon which is mounted asuitable pen, and an index pointer I4.

Connected to the armature 9 by a link I5 is a lever l6, pivoted at I1,and provided with an adjustable counterweight ll to counterbalance theweight of the armature 9. A curved member 59' is attached to the leverl6 and has adjustably secured to it one end' of a link 2. the other endof which is attached to one arm of a yoke shaped lever 2|. This lever ispivoted on a shaft 22 attached to the casing "I, and has one. arm of theyoke extending forwardly through the plat A and attached to the pen arml3. Therefore as the armature 9 moves in response to changes in modifiedform of control 2 flow the pen arm I! will be moved around an axis.

coincident with' shaft 22. The pen on arm I3 is adapted to make a recordon a suitable chart that is placed on the plate II and rotated by charthub I2. The chart hub is driven at a speed of one revolution everytwenty-four hours (or other time interval) by a synchronous motor 23located within the casing Ill.

Movement of the link also gives a corresponding movement to a lever 24by means of a short link 25 connected to that lever and member 2|. Thelever 24 is pivoted around a normally stationary, but adjustable fulcrumpoint 26 carried by a supporting lever 21 which may be adjustable as'hereinafter described. Movements of the lever 24 are transmitted to avalve actuating element 28 by a connecting link 29 to.

therebyefl'ect a corresponding initial control force adjustment of aport throttling element of a control valve.

The control apparatus through which the longitudinal movements of thelink 29 produce control effects by giving movements to the actuatingelement 28 may take various forms. As shown, the control apparatus is anair actuated controller of a form which is fully disclosed in my PatentNumber 2,125,081, dated July 26, 1938, and is now in extensivecommercial use. The lever 28 is pivoted at 30 to an adjustable fulcrummember 3| in the form of a lever having a stationary fulcrum pivot 32.The movements of the lever 28 produce control effects by moving aflapper valve 33 away from or permitting it to approach a nozzle orbleed orifice member 34.

The flapper valve 33 is mounted on a stationary pivot 35 and is biasedfor movement in the direction in which it approaches and restricts thedischarge through the nozzle 34. The lever acts on the flapper 34through a pin 38 carried by a depending arm of the lever.

The nozzle 34 receives air from a pipe 31 supplying air at a suitableand approximately constant pressure, through a restricted passage formedby a small bore pipe 49 included in a pilot valve mechanism 38, so thatthe pressure in the nozzle 34, which constitutes the primary controlpressure of the control apparatus, increases and decreases as theflapper valve 33 moves toward and away from the nozzle.

The ultimate control pressure is transmitted by a pipe 39 to the deviceto be controlled which,

as shown is the fluid pressure valve 2 controlling the flow in pipe I.The ultimate control pressureis also transmitted by pipe 40 to mechanism3i forming a part of the control apparatus of Fig. 1, and adapted,following and as a result of each change in the ultimate controlpressure effected through link 29, to give the lever 28 an initialfollow-up adjustment and a delayed compensating adjustment. Thefollow-up adjustment neutralizes a portion of the initial adjustment ofthe flapper valve 33 cffected by the link 29. The: delayed compensatingadjustment slowly neutralizes more or less of the effect of thepreceding follow-up adjustment.

The mechanism 4| comprises bellows elements,

two of which are connected. by a connecting rod and a pin' interposedbetween the levers 44 and 3|. The pin 45 is supported by a memher 4]adjustable to vary the leverage with which the lever 44 acts on thelever 3|. The

'in axial alignment with the stud 53.

latter is biased for movement in the clockwise direction, as seen inFig. 1.

Details of the construction and operation oi the mechanism, notspecifically referred to herein, will be understood by those skilled inthe art from the drawings, and need not be described herein,particularly as that mechanism is not only fully disclosed in said priorPatent 2,125,081, but is in extensive use. Moreover, the particular formof the control apparatus actuated by the longitudinal movements of thelink 29 forms no part of the present invention, though it is anadvantage of the present invention that it permits the ready combinationwith a measuring instrument of the character disclosed.

The pilot valve mechanism 38 used with this embodiment of the inventionis of novel design.

Air under a constant pressure is supplied from some suitable sourcethrough a conduit 48 and a small line 49 containing a pressure reducingrestriction 49' to a chamber A formed of a cap 50 attached to astationary plate 5| and a bellows 52 that is also'at'tached to theplate. A

small opening in the plate is provided so the.

conduit 31 leading to the bleed nozzle 34 may also be connected to thechamber formed bediaphragm of valve 2 and to efiect the adjustment ofthe control apparatus 40.

Rigidly connected with the bellows is a hollow stud 53 whose openingcommunicates with a second chamber B formed between the bellows 52 and abellows 54, also attached to the plate 5|. This chamber B is incommunication with the atmosphere by means of small openings in theplate 5|. As shown the plate 5| is supported by a casting 55 that has anopening in it Secured to the stud 53 and extending through the openingin the casting is a hollow exhaust nozzle 56v which also passes throughan opening in a guide and flapper supporting plate 51. A flapper 55 ispivotally mounted on the plate 51 and has a normal counterclockwise biasinto engagement with the end of nozzle 56 and-with a nozzle 53 that isin direct communication with the air supply conduit 48. As is best shownin Fig. 2 a chamber'C formed in the casting 55 to'the left of plate 51is in communication with the conduit 40 leading to the control mechanism4|.

The space in the casting 55 to the right of the plate 51 is incommunication with the interior of bellows 54, and, as shown, in Fig. 2,is directly As is best shown in the enlarged views of into a land 6|which is circular in shape and the size of the outside diameter of thenozzle. The land is of a width equal to the thickness of the plate 51.In a position of equilibrium the bellows 52 is of such a length thatnozzle 55 is positioned with its *land 5| in line with plate 51 and withflapper 58 covering both .of the nozzles 56 and 59. In this position asmall amount of air can leak between the nozzle 55 and plate 51 toequalize the pressures in'chamber C and conduit connected to the conduit39 leading to the valve .2 also begins to fall ofi, but at 39. In normaloperation of the device for small movement of the nozzle 56 air can leakslowly past the plate 51 to equalize the pressures in chamber C and thevalve 2, but for large movements of the nozzle, equalization may takeplace rapidly since the cut-out portions 60 permit air to flow readilybetween chamber C and the valve.

The tip of nozzle G is made detachable so that under some circumstancesa nozzle without the land 6| on it may be used.

It is noted that the pipe 40 is not connected directly to the line 31,and thereby subjected directly to the variable pressure produced bychanges in the flow. The reason for this is that the pressure in line 31is kept at a relatively low value for purposes of obtainihgproper nozzlecharacteristics and to minimize the valve leakage. Furthermore arelatively large amount of power is necessary to adjust the instrument4| and the valve 2. This power may be easily obtained by using air at ahigher pressure than it is desirable to use in the line 31. Thenecessary pressure differential between that used in line 31 and theconduits 39 and 40 is obtained by having the bellows 52 and 54 of thepilot valve formed of different areas. 'I'heratio ofthe two bellows isusually live to one, but may be made at any other desirable value.

In the operation of the system an increase in flow through the conduit Iwill cause the armatureitoriseinthe coils 1,111. Thisintum causesarmature 3 to rise and through lever l6, link 20 and lever 2| moves thepen arm IS in a counter-clockwise direction to indicate on the -chart anincrease in the flow. This same movement of lever 2| will, through lever24, lower link 29 to turn member 28 clockwise so that pin 36 may moveflapper valve 33 away from nozzle 34 thus permitting more air to escapethrough the nozzle and reduce the pressure in chamber A. As pressure inA reduces the bellows 52 will elongate to shift the nozzle 55 to' theright away from flapper 58. Air may therefore escape from chamber Cthrough the nozzle to chamber B and the atmosphere. As the pressure inchamber C is reduced the follow-up action of the instrument 41 willimmediately begin due to the reduction of air pressure in its left handbellows chamber. This follow-up action may proceed at a relatively rapidrate due to the fact that the nozzle 55 extends directly into chamber C.At the same time the nozzle 55 moves to the; right to permit reductionof pressure in chamber C, the pressure the valve action and permit thecontrol unit 4| to balance out before the valve pressure has had achance to overshoot. I

It should be noted that the difference in the lag effect on the controlaction due to large and small changes in the flow is of considerableimportance. On large changes in flow the valve 2 must be adjustedquickly and a large supply of air is admitted by the pilot valve intoconduit 39. This rapidly acts on the ,valve 2 even though the volume ofconduit 39 is relatively large. For small changes in flow the necessityfor rapid adjustment of valve 2 is not so great as before and it istherefore possible to slow up its action. The action of the controlvalve 2 under small changes in flow is further retarded since the effectof the capacity of conduit 39 is more pronounced. In other words a largepressure change in chamber C will have its effect transmitted morerapidly to control valve 2 than will a small pressure change, and. thespeed of transmission will slow down as the control valve 2 approachesits new position and the nozzle approaches the position where land 6| isin alignment with plate 51. V

For an initial reduction of flow the operation of the system would beopposite to the operation just. described, as will be obvious. It isnoted, however, that upon a movement of nozzle. to the left the flapper51 will be moved clockwise to uncover nozzle. 59. In this manner airfrom a the conduit 48 will be admitted to increase the pressure inchamber C and the valve 2.

The previously-mentioned adjustments of the fulcrum pin pivot 26 of thelever 24 are effected by adjustment of the'lever 21 about its supportingshaft 62 which is coaxial with shaft 22. As

I shown, the lever 21 is adjusted by rotation of a knob 63 mounted inthe instrument framework and frictionally held in any position-to whichit is adjusted. The knob 63 carries a crank arm 64 connected by a linkto a yoke extension of the lever 21. One leg of the yoke is extended toform an index or pointer l4 which indicates on I the chart the normalvalue of flow that the con- 50 from the center of the chart. By changingthe in conduit 39 and upon the diaphragm of valve a slower rate. Thisreduced rate is due to the comparatively slow leakage of air past plate51 into the chamber C. Thus the valve 2 is permitted toclose slowly.

In this manner the control unit 4| will first take its correct positionin response to a change in flow before the pressure change in thechamber C has had its full effect on the valve 2. Accordingly pulsationsin the flow will be eliminated. When the change in flow is small theabove operation will take place. When, however, the increase in flow islarge the flapper will be moved a greater distance from the nozzle 34and a larger reduction of pressure will take place in chamber A. Thenozzle 55 will therefore move to its extreme right hand position which,due to the cutout portions 60, will open the chamber C to the valve togive a quick response for changing the flow toward normal. As thebalanced position is approached, the connection between the chamber Cand the valve will be restricted to slow down trol apparatus is intendedto maintain. When the actual value of the flow is equal to the normalvalue, as indicated by the pointer l4, the end of pen arm I 3 will bethe same radial distance setting of pointer l4 in the above-describedmanner, the relation of various parts of the control apparatus will bealtered in such a manner that adjustments of the valve will maintaindifferent values of flow in pipe I.

In the embodiment of the invention disclosed in Fig. 5 the same resultis accomplished in a difierent manner. Air is supplied from pipe 48 .ata suitable constant pressure to a pilot valve 66. The air passes througha restricted passage formed'by a small bore nozzle 36. The primarycontrol pressure is transmitted by a pipe 68 to a chamber D of the pilotvalve. One wall 59 of the chamber D is movable and is formed of a pairof bellows having different areas to obtain the proper pressuredifierential between the chamber D and a chamber E on the other side ofthe wall. The pressure in the latter chamber is regulated by a valve 10actuated by the movable wall 69, and operating between exhaust port 10aand supply port 10b. The pressure in the chamber E is thus main- 15-tained in constant proportion to the control prespipe 61 included inthe pilot valve mechanism, through the line 31 to sure in chamber D andconstitutes the pressure applied to the instrument 4! through line 88.

In the system of Fig. 5 the pressure in the line 31 supplying air tonozzle 34 is used to control a second pilot valve 16 which regulates theair to the control valve 2.

The pilot valve 18 comprises a stationary casting 11 to which isattached a cover member 18 having an annular partition Ill extendingaround its interior. Attached-to the partition is a bellows 8|] thatforms between its exterior and the cover 18 a chamber. I-I. Fastened tothe lower side of the partition 19 is a second bellows 8|, preferablyenough smaller than the bellows 80 so that there is a ratio between thebellows equal to the ratio between the two bellows forming the movablewall 69 between chambers D and E in the pilot valve 68. The end walls ofthe bellows 88 and 8| are constrained for movement together by a post 82rigidly attached to the end wall of each; the post being provided withan opening 88 extending frombelow bellows 8| to the interior thereof,which is in turn in communication with the atmosphereby means of anopening 88 in the partition 18.

Mounted in a chamber J, formed in the casting TI, is a flapper valve 85which is spring biased in a counter-clockwise direction and has attachedto it a rod 86 that extends into the-opening 88 in the post 82. due topressure changes in the chamber H the rod 88 will serve to open or closethe opening 83. As the pressure in chamber H decreases the bellows 80will expand and move post 82 upwardly to open the port 83 and permitchamber J to communicate with the atmosphere. when, however, pressure inchamber H increases the bellows 88 will contract-and post 82 will bemoved As the post moves up or down and between the pilot valve and thecontrol valve. In either case a novel non-leak pilot valve such as isshown at 38 and 16 may be used.

While in accordance with the provisions of the statutes, I haveillustrated and described the best form of my invention now known to me,it will be apparent to those skilled in the art that changes may be madein the form of the apparatus disclosed without departing from the spiritof my invention as set forth in the appended claims, and that in somecases certain features of my invention may sometimes be used toadvantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a measuring and control instrument, a pilot valve having incombination, a movable nozzle, a pair of chambers separated by a wall,said nozzle extending through said wall and being so configured relativethereto that small movement thereof in either direction will permit asmall amount of leakage past the wall and large move.-

downwardly. This moves the rod 88 into the opening 83- to close thatopening and moves, through rod 88, theflapper 85 clockwise against itsbias to open a nozzle 81 that is connected with the air supply 48 bymeans of the pipe "ll. The chamber J is also in communication with thevalve 2 by means of the pipe 88.

In the operation of the embodiment of the system a movement of flapper 33 relative to nozzle 38 will vary the leakage through the nozzle andtherefore the pressure in chambers D and H of pilot valves 68 and 18,respectively. Change of pressure in chamber D will vary the position ofvalve Ill and thereby change'the pressure applied to the bellows chamberof instrument 8| in a manner previously described. The correspondingchange in pressure in the chamber H will either open chamber J to theatmosphere or permit air under pressure to enter from pipe 14."

Thus the pressure applied to the bellows chamber of the instrument M andthe diaphragm of ,the valve 2 will be changed, but the volume of airdelivered from the pilot valve, is so small compared tothat delivered bythe pilot valve 18' that the instrument 4| can rebalance itself morequickly than the control valve 2 is adjusted.

From the above detailed descriptionit will be seen that the differencein time of response of the. measuring and control components of acontrol system is taken into account in order to obtain a control actionthat is free from oscillations of the controlled medium. This may bedone either by varying the speed with which the control pressure isapplied to the instrument relative to that with which it is applied tothecontrol valve or may be done by varying the volume of air'between thepilot valve and the instrument ments in either direction will permit alarger amount of leakage therethrough.

2. In a measuringand control instrument, a pilot valve comprising incombination a chamber having a movable wall responsive to pressurevariations, a second chamber having a port communicatingwith a source ofpressure, a port attachedto and'mo'vable with said movable wall. thesecond port communicating withthe atmosphere, means in said secondto'normally close both ports, said means being moved m e direction bymovement of the f open the first port upon movementin'saiklj nedirection of said wall, and movement or in the opposite directionserving toopen said'eec'-' and port.

3. In a measuring and control instrument, a pilot valve operated inresponse to measurements made of a condition to be controlled, saidPilot valve comprising a 'moveable wall, a port meniber movable by saidwall, first and second chambers divided by a partition wall throughwhich said port member extends, an air supply for one of said chambersadjusted by movement of said port member, said port member being soconfigured relative to said partition wall where it passes through thesame that movement of the port member in either direction regulates flowof air fromsaid one of said chambers to the other.

4. In a measuring and control instrument, a pilot valve having a,moveable wall, a tubular member attached thereto, a pair of chambersseparated by a partition, said member extendin through the partitionfrom one chamber to the other, a, supply of fluid under pressure forsaid other chamber, valve means to close the openin of said member andshut off the air supply, said member and partition being so relativelyconfigured that fluid may travel from one chamber to the other at alltimes and in an amount depending upon their relative positions.

5. A non-leak pilot valve comprising in combination a chamber, a port insaid chamber for supply of fluid under pressure, an exhaust port in saidchamber, a pivoted valve member adapted to simultaneously cover both ofsaid ports, and means to move said valve relative to said portscomprising as a. part thereof one of saidports.

6. A measuring and control instrument, a pilot valve having incombination a chamber one wall latter moves, and a closure member forsaid port attached to said valve said port moving into and out ofengagement with said closure to control the flow or air through saidport and said air supply.

7. A non-leak pilot valve comprising a chamher, inlet and exhaust portscommunicating with said chamber, one of said ports being movablerelative to the other, common closure means for said ports, said closuremeans being constructed and arranged to close one or the other or bothof said ports depending upon the position of said movable one of saidports, and pressure responsive means arranged to move the movable one ofsaid ports from a, position in which both ports are closed to a positionin which'one or the other of the ports is closed depending upon whetherthe pressure acting on said -pressure responsive means is increased ordecreased.

- COLEMAN B. MOORE.

